CN114402015A

CN114402015A - Combined recycling method of composite material based on thermoplastic polymer matrix

Info

Publication number: CN114402015A
Application number: CN202080067028.0A
Authority: CN
Inventors: J-L·迪博瓦
Original assignee: Arkema France SA
Current assignee: Arkema France SA
Priority date: 2019-09-26
Filing date: 2020-09-25
Publication date: 2022-04-26
Anticipated expiration: 2040-09-25
Also published as: JP2022549715A; CN114402015B; FR3101351B1; BR112022003483A2; MX2022003198A; EP4034592A2; US20220324140A1; WO2021058923A3; FR3101351A1; WO2021058923A2; KR20220068995A

Abstract

The invention relates to a method (100) for recycling a first article (10) to be recycled, comprising a composite material based on a fibrous reinforcement and a thermoplastic polymer, preferably a (meth) acrylic polymer matrix, characterized in that it comprises the following steps: -introducing (130) a first article (10) into a system (1) suitable for recycling thermoplastic polymers, -introducing (140) a second article (20) to be recycled into a system (1) suitable for recycling thermoplastic polymers, which second article (20) to be recycled comprises thermoplastic polymer resin but no fibrous reinforcement, -heating (150), in said system (1) suitable for recycling thermoplastic polymers, the article (10, 20) to be recycled at a given temperature to depolymerize the thermoplastic polymer, preferably a (meth) acrylic polymer, and form the base monomer of said thermoplastic polymer, and-recovering (160) the constituent base monomers of said thermoplastic polymer.

Description

Combined recycling method of composite material based on thermoplastic polymer matrix

[ technical field ]

The present invention relates generally to recycling of articles made of composite materials based on a thermoplastic polymer matrix, and in particular to a method for recycling articles made of composite materials based on a fibrous reinforcement and a thermoplastic polymer matrix, such as in particular a (meth) acrylic thermoplastic polymer. The invention also relates to a system for recycling articles made of composite material that can implement such a method.

The invention can be used in the industrial sector facing the problem of recycling the following species: having a thermoplastic polymer matrix, in particular a (meth) acrylic thermoplastic polymer matrix, a post-consumer product such as a scrap product, or an industrial waste such as a defective product or a residue from a plastic processing operation.

[ Prior Art ]

Composite materials are widely used in different industrial sectors: the transportation (motor vehicles, railways), sports leisure, health, wind power, navigation or aviation sector. These composite materials (also abbreviated as "composites") are macroscopic combinations of at least two mutually immiscible materials. Typically, the composite material consists of a polymer matrix forming a continuous phase on the one hand, and a reinforcement material (or reinforcement), typically a fibrous reinforcement, on the other hand. There are also composites consisting of a polymer matrix and a mineral filler, such as quartz, marble, silica, aluminum hydroxide or titanium dioxide. Optionally, the composite further comprises an additive. In addition, these materials are often combined with other elements (e.g., metal inserts, wood, or foam) to make articles for use in various industries. Recycling of products is a significant challenge in the context of transitioning to recycling economies to efficiently utilize resources and reduce the impact of the product on the environment throughout its life.

Recycling of articles comprising composite materials based on polymer matrices or polymer composite materials can be carried out according to several methods. These processes generally involve thermal degradation of the polymer, i.e., an increase in the temperature of the polymer results in a loss of the mechanical and physical properties of the polymer, followed by depolymerization.

Pyrolysis is known and is a thermal process involving placing the article to be treated in a suitable chamber and then heating the chamber, thereby transferring heat to the article. The pyrolysis temperature is generally between 400 ℃ and 1300 ℃ to enable chemical decomposition of the polymer matrix. Pyrolysis of the article results in the formation of gases, oily residues and solid residues, including reinforcements for the composite, inorganic fillers and carbonaceous solids. The gases obtained after pyrolysis can be valorized for making new polymeric articles and the solid residues obtained after pyrolysis can be valorized for making other products, such as insulation. Such recycling processes generally have modest monomer (e.g., methyl methacrylate) yields. In fact, it is well known from the literature that composite materials lead to the formation of more residues and to poorer yields of monomers during pyrolysis than pure polymers.

Fluidized bed processes are also known, wherein the fluidized bed may be, for example, a silica sand bed. In such processes, articles comprising the composite material are typically pre-ground and placed in a fluidized bed reactor comprising a fluidized bed. Fluidization is carried out using a gas stream heated at a temperature generally above 400 ℃. In the bed, the matrix is rapidly heated and vaporized, thereby removing the reinforcement material from the matrix. A portion of the reinforcement material is then carried out of the bed in a stream of gas to a second combustion chamber. Another portion is entrained with the solids making up the fluidized bed and carried into a vessel where the solids are reheated and the carbonaceous residue is burned before being returned to the fluidized bed reactor. As with pyrolysis, the process is not designed to optimize the yield of monomer.

In particular, poly (methyl methacrylate) (PMMA) is a mature thermoplastic polymer and is known for its optical properties. For example, PMMA sold under the name Altuglas produces about 30 million tons per year in Europe. Although PMMA can be converted to monomer by thermal depolymerization, only about 30000 tons of PMMA waste are collected annually in europe for recycling. Furthermore, to a large extent, the recycling of PMMA currently in europe is based on the lead process (molten lead bed), which does not allow to reprocess poor PMMA (e.g. in the form of composites or high additives) because these poor grades lead to the formation of large residues and to low monomer yields.

It appears that the known recycling processes for articles comprising composite materials comprise various heating steps which do not allow the formation of monomers in high yields, in particular in the presence of fibrous composite materials.

From an energy and environmental point of view, it is therefore desirable to provide a recycling process which allows to increase the monomer formation yield during recycling of a fibrous composite based on a thermoplastic polymer matrix, such as (meth) acrylic acid.

[ problem ] to

The object of the present invention is to overcome the drawbacks of the prior art. The invention is particularly aimed at proposing a simple and effective solution for depolymerizing the constituent polymers of articles made of composite materials based on fibrous reinforcements.

[ brief summary of the invention ]

To this end, the invention relates to a recycling process for a first article to be recycled, comprising a composite material based on a fibrous reinforcement and a thermoplastic polymer matrix, preferably (meth) acrylic acid, characterized in that said recycling process comprises the following steps:

-introducing the first article to be recycled into a system suitable for recycling thermoplastic polymers,

introducing a second article to be recycled into a system suitable for recycling thermoplastic polymers, the article comprising a thermoplastic polymer resin, preferably a (meth) acrylic polymer, and not comprising any fibrous reinforcement,

-heating the article to be recycled at a given temperature in said system suitable for recycling thermoplastic polymers, to depolymerize the thermoplastic polymers, preferably (meth) acrylic polymers, and form the base monomers of said thermoplastic polymers, and

-recovering the constituent base monomers of the thermoplastic polymer.

As will be detailed below and in the examples, this process allows to increase the yield of the base monomer.

According to other optional features of the method:

it comprises a step of purifying the base monomer previously recovered. In fact, considering that the thermoplastic polymers of the first and second articles to be recycled may be different, the process according to the invention may result in the production of a plurality of monomers which will be able to be separated in a purification step (for example distillation). In fact, although the first and second articles to be recycled each comprise a polymer, preferably a (meth) acrylic polymer, they may comprise different comonomers and different additives.

It comprises a step of removing the solid components produced during the step of heating the first and second articles to be recycled. This allows the recirculation system to be cleaned of solid materials that may impair performance, particularly in the case of continuous recirculation systems, given the presence of fibrous reinforcement and optional fillers.

-the thermoplastic polymer matrix of the first article is a poly (methyl methacrylate) matrix. Poly (methyl methacrylate) which can be depolymerized to Methyl Methacrylate (MMA) is particularly suitable for the process according to the invention.

-the first product to be recycled and the second product to be recycled are introduced in a mass ratio of 0.1 to 1.5, preferably 0.1 to 0.5, more preferably 0.2 to 0.4. As shown in the examples, such a ratio can significantly improve yield.

The first article to be recycled has a mass percentage of fibrous reinforcement greater than 30%, preferably greater than 50%, more preferably greater than 70%. The higher the mass percentage of fibrous reinforcement in the article to be recycled, the lower the base monomer recovery is generally. However, under these low yield conditions, the gain allowed by the process according to the invention is high. Thus, although this type of material is difficult to recycle by conventional techniques, the method according to the invention has significant advantages. In particular, the mass percentage of the fibrous reinforcement corresponds here to the mass of the fibrous reinforcement in the first article to be recycled relative to the total mass of the first article to be recycled.

The second article to be recycled is in the form of a slurry at room temperature (for example 25 ℃) and has a mass percentage of equivalent thermoplastic monomers, preferably (meth) acrylic monomers, greater than 80%, preferably greater than 90%, preferably greater than 95%.

In another embodiment, the second article to be recycled has an equivalent weight of (meth) acrylic monomer of less than 95%, preferably less than 90%, preferably less than 80%, more preferably less than 70%. In fact, although the invention may work with cast sheets of substantially pure methacrylic thermoplastic polymer, when the second article has reinforcements, additives or fillers, the invention allows to obtain a higher gain in the combined recovery of the base monomers without a significant reduction in purity.

In another embodiment, the second article to be recycled has a mass percentage of equivalent weight methyl methacrylate monomers of less than 95%, preferably less than 90%, preferably less than 80%, more preferably less than 70%. As previously mentioned, the present invention allows for a higher gain in the combined recycle yield of the base monomer when the second article has a polymer or copolymer that is not based on methyl methacrylate. This is particularly advantageous when the thermoplastic polymer matrix of the first article to be recycled is PMMA.

-the system suitable for recycling the thermoplastic polymer is selected from:

an extruder and/or a conveyor belt depolymerization system,

a drum depolymerization system, and

depolymerization system on hot plate, preferably continuous.

-during the heating step, the first and second articles to be recycled are heated to a temperature between 200 ℃ and 1500 ℃, preferably to a temperature between 200 ℃ and 600 ℃, and advantageously to a temperature between 300 ℃ and 600 ℃.

It also comprises moderate heating of thermoplastic polymers, preferably (meth) acrylic polymers, to at least partially liquefy them. This moderate heating allows liquefaction without depolymerization. During moderate heating, the thermoplastic polymer, preferably the (meth) acrylic polymer, is heated to a temperature between 200 ℃ and 350 ℃, preferably to a temperature between 200 ℃ and 325 ℃, advantageously to a temperature between 225 ℃ and 300 ℃. It can be carried out at a temperature substantially equal to 270 ℃; such temperatures must be sufficient to allow the liquefied thermoplastic polymer to move. The mild heating may be mild heating of the second article or mild heating of the second and first articles to be recycled. Moderate heating can improve yield gain.

-recovering the fibrous reinforcement of the first article to be recycled, said recovering being carried out by at least one of the following methods: centrifugation, draining, spin-drying, pressing, filtering, screening and/or cyclonic separation. During heating of the article to be recycled containing the fibrous reinforcement, the polymer matrix of the article may be separated to recover the fibrous reinforcement, to increase the purity of the monomer recovered thereafter, and optionally to reuse the fibrous reinforcement without degrading it.

The invention also relates to a recycling system for a first article to be recycled, the article comprising a composite material based on a fibrous reinforcement and a matrix of a thermoplastic polymer, preferably a (meth) acrylic polymer, the system comprising:

means for conveying the first article to be recycled,

a device for conveying a second article to be recycled, the second article to be recycled comprising a thermoplastic polymer, preferably a (meth) acrylic polymer resin, and not comprising any fibrous reinforcement, and

a reactor suitable for heating the article to be recycled and depolymerizing a thermoplastic polymer, preferably a (meth) acrylic polymer, and forming the base monomers of the thermoplastic polymer.

Advantageously, but not in a limiting way, the recycling system according to the invention comprises a second reactor suitable for moderate heating of one of the products to be recycled, preferably of a second product to be recycled, said second reactor comprising an opening arranged for fluid communication with the first reactor.

In a particular embodiment, the recycling system according to the invention comprises means for recovering the constituent basic monomers of the thermoplastic polymer.

In a preferred embodiment, the recycling system according to the invention comprises means for moving said first and second articles to be recycled.

Further advantages and characteristics of the present invention will become apparent from reading the following description, given as illustrative and non-limiting examples, with reference to the accompanying drawings:

FIG. 1 shows a step diagram of a recycling process according to one embodiment of the present invention;

FIG. 2 shows an illustrative schematic view of an example of a recirculation system according to an embodiment of the invention;

FIG. 3 shows a schematic side sectional view showing an example of a recycling system comprising an extruder according to an embodiment of the present invention;

FIG. 4 shows a schematic side sectional view showing an example of a recirculation system comprising a heating support according to an embodiment of the invention; and

fig. 5 shows a schematic diagram showing a cross-sectional top view of an example of a recirculation system including a rotating drum according to an embodiment of the present invention.

Aspects of the invention are described with reference to flowchart illustrations and/or block diagrams of methods or systems (or devices) according to embodiments of the invention. In the drawings, flowcharts and block diagrams illustrate the architecture, functionality, and operation of possible implementations of systems and methods according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a system, device, or module for performing the specified logical function. In some embodiments, the functions associated with the blocks may occur out of the order shown in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved.

[ description of the invention ]

In the remainder of the description, the term "monomer" means a molecule that can undergo polymerization.

The term "polymerization" as used relates to a process of converting a monomer or a mixture of monomers into a polymer.

The term "polymer" refers to a copolymer or a homopolymer. "copolymer" is a polymer that combines a plurality of different monomer units, while "homopolymer" is a polymer that combines the same monomer units.

The term "depolymerization" as used relates to a process of converting a polymer into one or more monomers and/or oligomers and/or polymers having a molecular weight that is relatively small relative to the molecular weight of the original polymer.

The term "base monomer" refers to the most predominant monomer unit that makes up the polymer. Thus, in PMMA, the base monomer is MMA.

The term "thermoplastic polymer" or "thermoplastic" refers to a polymer that can soften or melt in a repetitive manner under the action of heat and take on a new shape by the application of heat and pressure. Examples of thermoplastics are for example: high Density Polyethylene (HDPE), mainly for the production of plastic bags or for automotive manufacturing; polyethylene terephthalate (PET) or polyvinyl chloride (PVC), in particular for the production of plastic bottles; polystyrene (PS) used in the packaging and construction industries; polymethyl methacrylate (PMMA). The use of thermoplastics therefore reaches a wide range of fields from packaging to the automotive industry and the demand for plastics is still high.

The term "thermoplastic monomer" refers to one or more monomers or molecules that are in the thermoplastic polymer chain after polymerization.

The term "(meth) acrylic thermoplastic polymer" or "(meth) acrylic polymer" refers to a homopolymer or copolymer based on (meth) acrylic monomers, for example selected from methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, methacrylic acid, acrylic acid, n-butyl acrylate, isobutyl acrylate, n-butyl methacrylate, isobutyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate and mixtures thereof. Poly (methyl methacrylate) (PMMA) is a specific example of a (methacrylic acid) polymer obtained by polymerization of methyl methacrylate monomers.

For the purposes of the present invention, the term "PMMA" denotes homopolymers and copolymers of Methyl Methacrylate (MMA), the weight ratio of MMA in PMMA preferably being at least 70% by weight of the MMA copolymer. The term "methyl methacrylate-based copolymer" refers to a copolymer containing at least one methyl methacrylate monomer. For example, the copolymer based on methyl methacrylate may be a copolymer comprising at least 70% by weight, preferably 80% by weight, advantageously 90% by weight, of MMA in PMMA.

The term "polymer matrix" refers to a polymer-based solid material used as a binder in the context of composite materials. The "matrix" comprises polymers and/or oligomers and may also comprise additives and/or fillers. Thus, "(meth) acrylic polymer matrix" refers to any type of matrix, including acrylic and methacrylic polymers, oligomers, or copolymers. However, if the (meth) acrylic polymer matrix comprises up to 49% by weight, preferably less than 40% by weight, of non-acrylic compounds, for example in the form of monomers, polymers, copolymers or block copolymers, for example selected from: lactic acid, butadiene, isoprene, styrene, substituted styrenes such as alpha-methyl styrene or t-butyl styrene, cyclosiloxanes, vinyl naphthalene, and vinyl pyridine, without departing from the scope of the invention.

For the purposes of the present invention, the term "polymer resin" corresponds to a solid material based on a polymer. "polymeric resins" comprise polymers and/or oligomers and may also include additives and/or fillers. The polymer resin may be in solid or liquid form (especially in slurry form). Additives and/or fillers may in particular improve certain properties, such as impact strength or heat resistance. Thus, "(meth) acrylic polymer resin" refers to any type of resin, including acrylic and methacrylic polymers, oligomers, or copolymers. However, if the (meth) acrylic polymer resin comprises up to 49% by weight, preferably less than 40% by weight, of non-acrylic compounds, for example in the form of monomers, polymers, copolymers or block copolymers, for example selected from: methacrylonitrile, lactic acid, butadiene, isoprene, styrene, substituted styrenes such as alpha-methyl styrene or tert-butyl styrene, cyclosiloxanes, vinyl naphthalene and vinyl pyridine without departing from the scope of the invention.

For the purposes of the present invention, the term "slurry" refers to a liquid composition having a dynamic viscosity at 25 ℃ of from 10mpa.s to 10000 mpa.s. The dynamic viscosity of the slurry is in the range from 10 to 10000, preferably from 20 to 7000, advantageously from 20 to 5000 mPa.s. The viscosity of the slurry can be easily measured with a rheometer or viscometer. The dynamic viscosity is measured at 25 ℃.

For the purposes of the present invention, the term "composite" refers to a multicomponent material comprising at least two immiscible components, at least one of which is a polymer and the other of which may be, for example, a reinforcement such as a fibrous reinforcement or filler.

The term "reinforcement" refers to a non-depolymerizable or vaporizable solid material, such as "fibrous reinforcement" or "mineral filler", that generally remains at the end of the recycling.

The term "fibrous reinforcement" refers to fibers, an aggregate of unidirectional rovings or a continuous filament mat, a fabric, a felt, or a non-woven fabric that may be in the form of a strip, a mesh, a braid, a strand, or a component. In the context of the present invention, a fibrous reinforcement will preferably correspond to a reinforcement comprising fibres having a length of more than 10mm, more preferably more than 20mm, even more preferably more than 3 cm.

The term "mineral filler" refers to all pulverulent fillers, such as quartz, marble, silica, aluminum hydroxide or titanium dioxide.

For the purposes of the present invention, the term "mass ratio" corresponds to the ratio with respect to the weight of the article to be recycled.

For the purposes of the present invention, the term "mass percentage of equivalent methacrylic monomer" corresponds to the theoretical mass content of methacrylic monomer relative to the total weight of the article to be recycled. This percentage is preferably calculated without taking into account the optional methacrylic moieties that may be contained in the fillers or additives present in the volume of the article. The theoretical mass of methacrylic monomer may correspond to the mass fraction of methacrylic monomer derived from the polymer or copolymer.

For the purposes of the present invention, the expression "at least partially liquefying the thermoplastic polymer" corresponds to the beginning of the step of at least partially melting the thermoplastic polymer contained in the article to be recycled (i.e. well above the glass transition temperature T)_gAnd/or melting point T_mThe latter being exclusively needle crystalline or semi-crystalline polymers). Depending on the polymer in question, the temperature must allow the molten thermoplastic polymer to have a viscosity sufficient to allow extrusion of the polymer without complete decomposition.

For the purposes of the present invention, the term "substantially equal" means a value which varies by less than 30%, preferably by less than 20%, even more preferably by less than 10%, with respect to the contrast.

In the following description of the embodiments and the accompanying drawings, the same reference numerals are used to designate the same elements or similar elements.

Recycling of materials, and even composite materials, requires consideration of many parameters so that the recycling has a more favorable carbon and energy balance than the energy balance of the initial manufacturing.

In particular, for the recycling of composite materials having a thermoplastic polymer, preferably a (meth) acrylic polymer matrix, the technical problem to be solved is to increase the productivity during the depolymerization of composite materials having a (meth) acrylic thermoplastic polymer matrix. In fact, the solution conventionally provided consists in increasing the depolymerization temperature. However, in the case of a (meth) acrylic thermoplastic polymer matrix, increasing the temperature has little effect on the rate of depolymerization.

Surprisingly, the inventors have found that when mixing a composite material with a thermoplastic polymer matrix of different grades, advantageously but not limitatively (meth) acrylic matrices, the yield of monomers obtained in a given period of time is improved. This means that the yield is higher than by depolymerising the two fractions independently in the same time period.

The inventors have therefore developed a process for recycling a composite material based on a thermoplastic polymer, preferably a (meth) acrylic polymer matrix, with improved monomer yield. As will be presented in the examples, the gain in yield is more pronounced for certain mass ratios between the composite and other grades of thermoplastic, preferably (meth) acrylic polymer matrix. In addition, a recycling system capable of carrying out such a method is also proposed.

The invention allows to obtain a satisfactory production of methyl methacrylate, in particular starting from materials based on (meth) acrylate matrices which can be recycled in small amounts (i.e. which have a low yield of methyl methacrylate production).

The invention therefore relates in particular to a recycling process for articles made of composite material. The article made of composite material, or the first article 10 to be recycled, may in particular be an article made of composite material based on a fibrous reinforcement and a thermoplastic polymer matrix, preferably a (meth) acrylic thermoplastic polymer matrix. In particular, it is to be noted that the product to be recycled may be a finished product or a part of a finished product at the end of its useful life, or waste generated in the production of such a product. In both cases, a prior sorting step may prove necessary to eliminate non-depolymerizable waste or any non-depolymerizable product that also results in a loss of energy efficiency.

The article made of composite material or the first article 10 to be recycled may also comprise other polymers than the thermoplastic polymer matrix of the composite material based on fibrous reinforcement. This may be an adhesive, foam, gel-coat or other polymer that is different in kind from the thermoplastic polymer matrix of the composite. In this case, the crushing step 105 may prove necessary upstream 105a or downstream 105b in order to remove or reduce the amount of these other polymers. Preferably, if the crushing step 105 occurs, it is performed upstream of the crushing step 105b, more preferably before the grinding step 110.

As previously mentioned, the fiber reinforcement-based composite has a yield of recycled monomer, whether in molar or mass yield, that is lower than the yield of non-composite (e.g., calculated after recovery of condensate and separation of the base monomer, based on the theoretical content of the base monomer). However, the present technique is particularly suitable for such materials. The mass yield of the recovered base monomer relative to the equivalent monomer can be calculated by taking into account the mass content of the monomer recovered from the condensate and the theoretical mass content of the monomer in the product to be recycled. However, a prerequisite for this calculation is the ability to determine the theoretical mass content of monomer in the recycled product. This is possible in certain controlled experiments, but has proven to be more difficult during industrial use of the present invention. Thus, in the examples, improvements in mass yield are mentioned. This is based on the increase in the mass of the base monomer recovered by using the process according to the invention compared to the mass of the base monomer recovered by the prior art technique.

In the composite material, the thermoplastic polymer matrix is intimately bonded to the reinforcement. A fibre reinforcement can be regarded as a reinforcement, typically based on glass fibres or carbon fibres. For example, the fibrous reinforcement may be a fabric, a mesh, a felt, or any other fibrous material. The fibrous reinforcement will be based on, for example, glass fibres, carbon fibres or basalt fibres, or metal or vegetable fibres.

The (meth) acrylic thermoplastic polymer may be a homopolymer or a copolymer based on (meth) acrylic monomers selected, for example, from methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, methacrylic acid, acrylic acid, n-butyl acrylate, isobutyl acrylate, n-butyl methacrylate, isobutyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate and mixtures thereof.

In particular, the composite material of the article to be recycled is based on PMMA and a fibrous reinforcement.

Figure 1 details the main steps of the recycling process according to the invention. In particular, the recycling method 100 according to the invention comprises introducing 130 a first article 10 to be recycled into a system 1 suitable for thermoplastic polymer recycling, introducing 140 a second article 20 to be recycled into the system 1 comprising a thermoplastic polymer resin, preferably a (meth) acrylic polymer resin, but not comprising any fibrous reinforcement, heating 150 the article to a given temperature and recovering 160 the constituent base monomers of the thermoplastic polymer, preferably a (meth) acrylic polymer. The second article 20 to be recycled may also contain additives to improve certain properties: such as impact strength, heat resistance. Typically, such additives can interfere with depolymerization.

The second article to be recycled may also be in slurry form at room temperature and have an equivalent weight of thermoplastic monomer, preferably (meth) acrylic monomer, of greater than 70%, for example greater than 75%, preferably greater than 80%, more preferably greater than 90%, even more preferably greater than 95% by mass. In fact, such a paste can be obtained during the preparation of the cast slab during the prepolymerization of methyl methacrylate or by dissolving PMMA in methyl methacrylate. Preferably, the polymerization inhibiting additive is added to the second article during use of the second article. Such additives may be hydroquinone, MEHQ (4-methoxyphenol), phenothiazine or Topanol (2, 4-dimethyl-6-tert-butylphenol). Such a slurry may advantageously, but not exclusively, be composed of Elium ® resin in liquid form.

Furthermore, as will be detailed below, the method 100 according to the present invention may include a crushing step 105 of the previously recovered base monomer, a grinding step 110, a sorting step 120, a purification step 170, and a removal step 180 of solid components generated during the heating step.

The present invention includes the combined recycling of two articles having different grades. In particular, the first article is a composite material comprising fibrous reinforcement, while the second article does not comprise any fibrous reinforcement.

Furthermore, as will be detailed below, it is in particular this combination of materials with different grades that allows the present invention to achieve higher monomer yields than those of these separately recycled materials. The invention thus makes it possible to achieve the correct monomer yield, i.e.a yield which is at least higher than that of materials which are separately recycled from materials which are generally regarded as recyclable in small amounts.

Ratings systems are inherent in the industry that specializes in material manufacture, particularly composite material manufacture. This system allows to reflect the quality of the material, partly its composition. Thus, the grade of the material will be affected by factors such as:

the presence or absence of reinforcements, and the type of reinforcement used,

characteristics of the matrix used: the polymer or possible combination of polymers forming the matrix, e.g. the presence or absence of cross-linking, and

-the presence or absence of additives.

Thus, in the context of the present invention, the first article 10 to be recycled preferably has a first grade, while the second article 20 to be recycled has a second grade different from the first grade.

In particular, the first article 10 to be recycled comprises fibrous reinforcement, while the second article 20 to be recycled does not comprise any fibrous reinforcement.

The first article 10 to be recycled and the second article 20 to be recycled may include additives such as plastic additives, additives for improving heat resistance, additives for improving impact strength, comonomers such as acrylates or other additives for blocking/slowing depolymerization. They may also include mineral fillers such as alumina, quartz, marble, aluminum hydroxide, and titanium oxide. In particular, the thermoplastic polymer, preferably the (meth) acrylic thermoplastic polymer, may comprise at least one additive, such as stabilizers, pigments, plasticizers, such as phthalates, adhesion promoters, uv absorbers, antioxidants, flame retardants, dyes, lubricants, mold release agents, antistatic agents, bactericides, surfactants and/or crosslinked polymer beads, impact strength additives, and the like. Indeed, the addition of additives generally allows to enhance the properties of the thermoplastic composition. For example, fillers improve chemical or heat resistance, plasticizers allow for reduced stiffness, stabilizers prevent polymer degradation, antistatic agents prevent dust deposition, lubricants limit wear, flame retardants provide better fire resistance, and the like. However, the presence of these additives generally indicates a lower yield of recovered base monomer in the case of recycling by depolymerization.

Preferably, the second article 20 to be recycled comprises at least 50 mass% of a thermoplastic polymer, such as a (meth) acrylic polymer, more preferably at least 60 mass% of a thermoplastic polymer, such as a (meth) acrylic polymer, even more preferably at least 70 mass% of a thermoplastic polymer, such as a (meth) acrylic polymer.

In addition, the second article 20 to be recycled is advantageously not an article that is generally considered to be readily recyclable. Thus, it may preferably comprise at least 5 mass% of filler (e.g. mineral filler), more preferably at least 10 mass% of filler, even more preferably at least 15 mass% of filler.

In a particular embodiment, the second article 20 to be recycled comprises at least 0.5 to 25 mass%, preferably 1 to 10 mass%, of an acrylic or non-acrylic comonomer.

Preferably, the second article 20 to be recycled comprises at least 5 mass% of additives, relative to the total weight of the thermoplastic composition, for example the (meth) acrylic composition, preferably at least 10 mass%, more preferably at least 15 mass%.

Preferably, the second article 20 to be recycled comprises at most 50 mass%, preferably less than 40 mass%, more preferably less than 30 mass%, even more preferably less than 25 mass% of additives relative to the total weight of the thermoplastic composition, for example the (meth) acrylic composition. Advantageously, but not limitatively, the second article 20 to be recycled comprises at most 50% by mass, preferably at most 25%, of additives of the following type: acrylic and/or methacrylate-butadiene-styrene impact modifiers and/or acrylic processing agents. The impact modifying additive serves to increase the impact strength of the thermoplastic material. In a particular embodiment, the second article 20 to be recycled comprises up to 30% of the polylactic acid-based additive. The polylactic acid-based additive is a thermoplastic resin derived from renewable plant resources, which has proven to be compostable. Such resins may also be combined with additives of the impact modifier type.

In particular, the second article 20 to be recycled may comprise an at least partially crosslinked thermoplastic polymer resin.

As shown in fig. 1, a recycling method 100 according to the present invention may include a preliminary sorting step 120. The sorting step may be a step in which the first article 10 to be recycled comprising the fiber reinforcement based composite material is separated and isolated. For example, it may be separate and isolated from an article that does not contain any composite material, and/or it may be separate and isolated from contaminants such as glass, sand, wood, other polymers, foam, or metal. The sorting step also allows the separation and sorting of plastics by the home. For example, thermoplastic polymers on the one hand and thermosetting polymers on the other hand can be sorted, and different thermoplastics can be sorted from one another. Sorting also allows eliminating the parts produced by grinding that are not made of composite material.

Sorting may be performed by any sorting method suitable for polymer recycling. One possible sorting method may involve a decantation system in which the waste is placed in a container of water and/or brine or organic liquid. The heavy elements are finally at the bottom of the container and can be discharged through a pneumatic airlock system. The elements to be recycled can be extracted from the container by means of a worm (at the top or bottom, depending on their density). Sorting may also include magnetic sorting to extract metal particles. Sorting may also include vortex separation(s) to remove certain metals, such as copper and aluminum. Separation techniques such as density sorting and magnetic separation in solution may also be combined. The sorting method may use spectroscopic techniques, such as raman or infrared, to identify the composition of the material. Sorting methods using the triboelectric properties of the material or its thermal adhesion properties may also be used. Sorting may be performed at a sorting center. The sorting step advantageously makes it possible to remove elements that may damage the various devices used in the implementation of the recycling method 100.

Furthermore, the article may be ground beforehand, for example in order to facilitate the introduction of the article into a reactor suitable for the recycling of the polymer. Thus, in one embodiment, the recycling method 100 for articles includes a step 110 of grinding articles performed prior to step 120 of FIG. 1, and in this case, the operation is facilitated because the sorting operation involves more pulverization than fine grinding. The grinding step makes it possible to reduce the size of the (first and/or second) article to be recycled and can be carried out, for example, using any suitable mechanical grinder. Non-contact grinding techniques may also be used. The first and second articles to be recycled are reduced to a size that allows the introduction of the abrasive material thus obtained into a device suitable for recycling according to the invention. The particles obtained after grinding may for example have dimensions (e.g. radius, diameter, median diameter, length, width, height) such that at least one dimension is between 1mm and 100mm, preferably between 3mm and 50 mm. Preferably, at least one dimension of the second article 20 to be recycled is less than 30 mm. At this time, the first and second articles to be recycled may take the form of chips, granules, or powders. More preferably, the grinding is carried out so that the second article to be recycled has at least one dimension thereof smaller than the largest dimension of the first article to be recycled. The first and second products to be recycled may also be present in the reactor in one or more of the forms described above. Advantageously, the grinding/pulverizing step 110 may facilitate the sorting step. However, it is generally easier to sort out large-sized pieces, provided that their composition is uniform. Thus, the purpose of the grinding operation is also to produce chips of uniform composition. That is why it can be performed before the sorting operation described above. The grinding operation may also be selective grinding.

As shown in fig. 1, the recycling method 100 according to the present invention comprises a step 140 of introducing the first article 10 into a system 1 suitable for recycling thermoplastic polymers. In particular, the first article 10 may be introduced into a reactor suitable for polymer recycling.

The first article 10 to be recycled can be introduced into the reactor, for example, by means of a worm screw, a conveyor belt, a hopper or by means of a metering module. The flow rate for feeding the first product 10 to be recycled to the reactor may be between 10kg/h and 2000kg/h, preferably between 50kg/h and 500kg/h, preferably between 100kg/h and 400 kg/h.

The recycling method 100 according to the invention also comprises a step 120 of introducing the second article 20 to be recycled into the system 1 suitable for thermoplastic polymer recycling.

The first article 10 and the second article 20 may be introduced into the system, in particular into the depolymerization reactor, either sequentially or simultaneously. Thus, the second article 20 to be recycled, which does not include any fibrous reinforcement, may be introduced before the first article 10 to be recycled.

Alternatively, the first article 10 and the second article 20 may be mixed and introduced simultaneously into the recycling system 1, in particular into a reactor suitable for recycling of the polymer. The first and

second articles

10, 20, for example, introduced in the form of granules, chips, needles, chips or powders, have significantly different particle sizes. Advantageously, the articles 10 to be recycled have a larger size than the articles 20 to be recycled. The method 100 may also include incorporating a variety of other articles, including thermoplastic polymers, preferably thermoplastic (meth) acrylic polymers.

Preferably, the first article 10 to be recycled, comprising a composite material based on fibrous reinforcement and a matrix of thermoplastic polymer, advantageously (meth) acrylic polymer, and the second article 20 to be recycled, based on a resin of thermoplastic polymer, preferably (meth) acrylic polymer (without fibrous reinforcement), are introduced in a mass ratio of between 0.1 and 1.5, preferably between 0.1 and 0.5, more preferably between 0.2 and 0.4 (second article/first article).

As shown in fig. 1, the recycling method 100 according to the present invention further includes a heating step 150 of the first and

second articles

10, 20. The heating may in particular be carried out in a reactor of the system 1, which is suitable for the recycling of thermoplastic polymers, preferably for the recycling of composite articles comprising thermoplastic polymers.

Preferably, the system 1 suitable for recycling thermoplastic polymer resins is selected from:

-a depolymerisation system in the form of an extruder/conveyor,

-a depolymerisation system in the form of a drum, and

depolymerization systems on a hot plate, for example continuous depolymerization systems.

The heating is carried out at a temperature that allows depolymerization of the thermoplastic polymer, preferably a (meth) acrylic polymer, and formation of the base monomers of the thermoplastic polymer of the first and

second articles

10, 20.

In particular, the heating of the article is carried out at a given temperature that allows the depolymerization of the thermoplastic polymer and the generation of the gaseous base monomer. The heating may be carried out, for example, at a temperature between 200 ℃ and 1500 ℃, preferably between 300 ℃ and 600 ℃, more preferably between 350 ℃ and 500 ℃ and even more preferably between 400 ℃ and 450 ℃. Heating may also be staged with a first heating zone at an intermediate temperature followed by a second or second heating zone, thus having multiple heating zones at elevated temperatures. The moderate temperature is preferably between 200-350 deg.C, more preferably between 200-300 deg.C.

In a preferred embodiment, the heating of the

articles

10, 20 to be recycled is carried out under an inert atmosphere, for example under vacuum, under nitrogen, under CO₂Under argon or under a substantially oxygen-lean atmosphere (e.g., containing 0.1% to 10% oxygen). Such an oxygen-depleted atmosphere may be obtained, for example, by recycling the combustion gases of the light effluent from the depolymerization unit.

Similarly, advantageously, the recycling method 100 for articles according to the invention comprises a step 151 of modest heating of the first and/or second article to be recycled. More preferably, the recycling method 100 according to the invention comprises a step 151 of mild heating of the second article to be recycled. The step of mildly heating the article to be recycled can be carried out before its introduction into the reactor and, where appropriate, after grinding. Mild heating may be carried out using any suitable heating device. In one variant, it may be initiated in a reactor suitable for the depolymerization of polymers. The temperature at which the article is preheated may be 50 ℃ or higher, for example 200 ℃. By subjecting the article to be recycled to mild heating, a portion of the polymer may be converted to a molten or liquid state and/or depolymerization of the polymer matrix may be promoted.

The recycling process 100 can result in the deconstruction of the polymer matrix and its transformation into a mixture, for example, in a molten or liquid state. Thus, the heating step 150 may include a fiber reinforcement recovery step 152. This step of recycling the fibrous reinforcement may be performed during the heating step or once said step is completed. In particular, once the monomer is recovered, the fiber reinforcement can be recovered.

As shown in fig. 1, the recycling method 100 according to the present invention further comprises a step 160 of recovering the constituent base monomers of the thermoplastic polymer, preferably the (meth) acrylic polymer.

Advantageously, the method 100 according to the invention may comprise a step of condensing these base monomers from the gaseous state to the liquid state to obtain a solution comprising the base monomers.

Preferably, the condensation may be carried out by contacting the gaseous monomer with the liquid monomer. Such contacting may be carried out, for example, in a shower-type device by spraying the liquid monomer (i.e., cold monomer) into a chamber of the collected gaseous base monomer (i.e., hot monomer). In this case, the device may comprise means for introducing a stabilizer or polymerization inhibitor.

Furthermore, the condensation of the gas mixture can be carried out in a fractional distillation mode and results in a cleaner fraction containing the base monomer and a less clean fraction containing the monomer and contaminants. The fraction containing contaminants may also be reintroduced into the reactor in order to allow a better separation of the monomers contained in the fraction.

The recycling process 100 according to the present invention may also comprise a purification step 170 of said previously recovered base monomer.

The purification step 170 may include a step of separation by distillation, for example, by a distillation column. In fact, during the depolymerization process, impurities may be formed, which subsequently need to be removed.

The recycling method 100 according to the present invention may further include a step 180 of removing solid components generated during the step of heating the first and

second articles

10, 20. The separation device for removing solid components is adapted to the state of the matrix in the reactor or at the reactor outlet, i.e. to the mixture being converted into the molten state or into the liquid state, or into the gaseous state, depending on whether the matrix is to be converted into the mixture. In the case where the reinforcement is contained in a mixture in a molten or liquid state, the separation device may be any device that allows solid/liquid separation, such as a grid. The separation may also be performed by centrifugation using a centrifuge, or by decantation, filtration, drainage, dehydration, pressing, or screening. Preferably, the separation is performed by filtration, pressing or decanting in a molten medium. In the case where the substrate is gasified/depolymerized, the gas phase separation means may comprise, for example, a cyclone or a filter. During use of the filter, back pressure is periodically applied to loosen solids accumulated on the filter. The solid filter cake is then recovered below the filter in a vessel provided for this purpose. Note that during matrix depolymerization, polymer residues may remain on the reinforcement, and solid phase separation of the solid residues may be performed by, for example, sieving (glass fiber/carbonaceous powder separation, etc.). This removal step advantageously makes it possible to treat the different types of solid residues formed during the depolymerization reaction, i.e. solid residues entrained in the gas phase and solid residues remaining dense (which will appear notably at the reactor outlet). Solid residues entrained in the gas phase potentially risk blocking the monomer condensation unit. These solid residues must therefore be filtered in the gas phase (for example by means of suitable separation devices: cyclones, filters) or in the liquid phase after condensation, while the solid residues emerging at the reactor outlet generally remain in the form of a solid mat which can be screened, for example for separating different solid residues. The hot solid residue must/can be cooled, for example by direct contact with water. During this cooling step, the direct contact between the solid and the monomer must be limited to prevent recondensation of the monomer directly on the solid.

According to another aspect, the invention relates to a system 1 for recycling a first article 10, the first article 10 comprising a composite material based on a reinforcement and a thermoplastic polymer matrix, preferably a (meth) acrylic polymer matrix.

As shown in fig. 2, the recycling system 1 according to the invention comprises means 11 for conveying a first article 10, the first article 10 comprising means 21 for conveying a second article 20 to be recycled, based on a fibrous reinforcement and a thermoplastic polymer matrix (for example a (meth) acrylate), the second article to be recycled comprising a thermoplastic polymer resin, preferably a (meth) acrylic polymer. The conveying means 11, 21 may be a pipe, a worm screw, a conveyor or hopper, a pneumatic conveyor, a vibrating conveyor or an extruder. Furthermore, they may be coupled to a metering device. The recycling system 1 according to the invention further comprises a reactor 50 adapted to heat the

articles

10, 20 to depolymerize the thermoplastic polymer, preferably the (meth) acrylic polymer, and form monomers. For example, heating can be carried out by exposing the article to microwaves, pulsed electric fields, or steam, or by contact with a hot surface, such as in an extruder, screw conveyor, drum, or the like. The hot surface may be heated in different ways: direct electrical heating, heat transfer fluid (steam, oil, molten salt, etc.) heating.

The recycling system 1 according to the invention also comprises means 60 for recovering the constituent monomers of the thermoplastic polymer, advantageously but not limited to a (meth) acrylic polymer.

Furthermore, the recycling system 1 according to the invention may comprise one or more devices for moving the first 10 and second 20 articles to be recycled, one or more video capture devices 356 (e.g. an infrared camera) as described in connection with fig. 4, one or more purification devices 70 and one or more solids removal devices 80.

The reactor of the system 1 according to the invention may be an extruder or a conveyor, a reactor suitable for pyrolysis, suitable for high-temperature pyrolysis, suitable for pyrolysis in a molten salt bath, or a fluidized bed reactor or a reactor suitable for solvolysis or other reactor consisting of hollow plates heated by a heat transfer fluid circulating in the plates. However, reactors have been identified which allow to increase the yield of monomers, such as: extruders, conveyors, extruder-conveyors, rotating drums, and/or heated plate sets.

The reactor suitable for recycling the thermoplastic polymer may also be a pyrolysis reactor, for example a multistage pyrolysis reactor or a stirred rotary cylinder reactor. Two configurations are possible: the cylinder rotates about its axis, or an internal stirring system ensures mixing and heat transfer from the wall to the polymer.

An extruder-conveyor is a reactor comprising one or more worms, each driven in a barrel, in particular allowing to stir the components introduced into said barrel. The use of an extruder-conveyor to perform the recycling process 100 is advantageous from the environmental, safety, and reliability standpoint of the process 100. In fact, the extruder-conveyor allows to handle high viscosity molten polymers without the need to add solvents to reduce the viscosity of the molten polymer. The extruder-conveyor has the advantage of allowing efficient heat transfer from the barrel to the composite material to be treated. The extruder may advantageously be replaced over all or part of its length by a screw conveying system. Advantageously, the system may comprise a combination of conveyor type devices in the first section followed by an extruder type device and terminated by a conveyor type device configured to convey solids (i.e. reinforcement) to the outlet. For example, the conveyor may be of the "screw" or "endless screw" type.

With reference to fig. 3, the recycling system 1 according to the invention may comprise an extruder, more specifically a twin-screw extruder 200 comprising an orifice 201 through which orifice 201 a first article 10 to be recycled comprising a composite material based on a fibrous reinforcement and a thermoplastic polymer, preferably a (meth) acrylate polymer matrix, may be inserted, for example, by means of a metering device 210 and a conveying device 211. Similarly, a second article 20 to be recycled may be inserted, for example by means of a metering device 220 and a conveying device 221, the second article 20 to be recycled comprising a thermoplastic polymer resin, preferably a (meth) acrylic polymer resin. The first and

second articles

10, 20 to be recycled may be in powder or granular form. Alternatively, the article may be introduced into the extruder after undergoing the first heating step.

Thus, the first and

second articles

10, 20 to be recycled are introduced hot or cold and may also be heated and/or maintained at temperature during processing.

The twin-screw extruder may be, for example, a Clextral type of extruder. The twin screw extruder includes two, most typically parallel screws 204 that rotate within a barrel 250. Advantageously, the extruder has adjustable features, i.e. the screw and barrel 250 are modules assembled in series, and the assembly thereof can be modified. Thus, barrel 250 here corresponds to a reactor of recirculation system 1 according to the invention suitable for

heating articles

10, 20 to depolymerize the thermoplastic polymer (a non-limiting example being a (meth) acrylic polymer). More generally, the reactor 50 of the system according to the invention can take different forms, provided that the gas flow and the temperature can be controlled.

In the extruder, the external heating device 255 that adjusts the temperature of the barrel 250 is advantageously configured to heat the first and

second articles

10, 20 to be recycled and bring the polymer matrix and the polymer resin into a molten state. The temperature in the reactor may be between 50 ℃ and 550 ℃ and it may be controlled by a temperature sensor not shown in the figure.

Depolymerization may produce products in gaseous form which are withdrawn from the extruder for processing. The solid residue, as such, is discharged by a suitable device 202. In particular, the reactor can be operated at reduced pressure or under a gas flow to convey the monomer formed to the condensation unit through the collection means. The generated gas may be directed through conduit 208 to a recovery unit 260 for condensation. The obtained condensate may then be collected in the chamber 209 for this purpose.

To allow recovery of the gas resulting from the implementation of the recycling process 100, a system 200.1 suitable for such recycling may comprise one or more purification devices. For example, the system may include a purification device not shown in the drawings, and the purification device may correspond to a system for separation by distillation, such as a distillation column. The distillation column allows separation of compounds according to their boiling points.

Another type of system that is advantageous for recycling the first article 10 comprises a composite material based on a fibrous reinforcement and a thermoplastic polymer (preferably (meth) acrylic acid) matrix, comprising a device consisting of hollow plates heated by a heat transfer fluid (pressure steam, oil, molten salt) line. During its treatment, the article is first advanced on a warming plate. The solid residue ends its passage through the reactor by passing over a plate of lower temperature, where heat exchange takes place from the residue to the heat transfer fluid. The heat transfer fluid thus heated can then be used to preheat the article at the reactor inlet.

Thus, in particular and with reference to the solution of fig. 4, the recirculation system 300 according to the invention comprises a casing 350 equipped with

heating plates

351, 352. The system comprises in particular two

containers

312, 322 which allow to store a first product 10 to be recycled and a second product 20 to be recycled, respectively. These containers are connected to the casing 350 by

ducts

311, 321 and make it possible to introduce therein said articles to be recycled, which are preferably previously ground/crushed/layered to a suitable granulometry. As shown in fig. 4, the system includes one or more heated supports 352 (e.g., heated plates), onto which heated supports 352 the second article 20 to be recycled is brought and configured to allow for the temperature of the thermoplastic polymer, which will begin to melt under the influence of the temperature before falling onto second heated support 351. Alternatively and according to a configuration not shown, the recycling system according to the invention is arranged to allow the first article 10 to be recycled to fall onto the second article 20 to be recycled, which has previously undergone a modest heating.

In addition, the system may include a motive device 355 (e.g., driven by a piston, blade, or claw) for urging the second article 20 toward the second heated support 351. As shown, a second heated support 351 (e.g., a heated plate) is arranged to receive and contact a first article 10 to be recycled with an at least partially melted second article 20 to be recycled. Furthermore, the second heating support 351 is configured to enable depolymerization of the polymer matrix under the effect of temperature. In the housing 350, the first and

second articles

10, 20 to be recycled are heated and the polymer matrix and resin are depolymerized at a regulated temperature by the heating supports 351, 352. The system is then configured to maintain a temperature sufficiently high to depolymerize the thermoplastic polymer, preferably a (meth) acrylic polymer. The temperature inside the housing may be between 50-550 c and it may be controlled by a temperature sensor not shown in fig. 4. The system may then be arranged to push the mixture of the first and

second products

10, 20 towards a third heated support (or a cascade of steps) or towards a separation device 381 (such as a screen or grid) which allows to separate the solid residues according to their diameter. For example, such a separation device may be used to separate the fibrous residue 15 from other fillers that may be included in the second article 20 to be recycled. Furthermore, the separating means 381 may be connected to movement means 382 (e.g. pistons, motors) which allow an improved and/or accelerated separation. The solid residue may then be removed by a suitable device 302.

In the reactor, the polymer, preferably a meth (acrylic) polymer, is depolymerized under the action of heat, in particular in the case of articles to be recycled consisting of a meth (acrylic) thermoplastic polymer in gaseous form, to produce methyl methacrylate monomers. The generated gas 358 may be directed to the cooling system 360 via a conduit 359 to be condensed. The condensate obtained can then be collected in a chamber for this purpose. The housing and chamber are preferably under negative pressure or gas flow to convey the monomer formed to the condensing unit. The condensation unit is more particularly capable of condensing the gaseous base monomer mixture. In addition, as previously described in connection with fig. 3, the reactor can be operated at a negative pressure or gas flow to convey the monomer formed to the condensation unit via the collection means. In particular, the generated gas may be directed to the recovery device 360 through a conduit 359 to be condensed. The obtained condensate may then be collected in a chamber 309 provided for this purpose. To allow recovery of the gas resulting from implementation of the recycling process 100, a system 300 suitable for recycling may include one or more purification devices. For example, the system may comprise a purification device, not shown in the figures, which may correspond to a system for separation by distillation, such as a distillation column. The distillation column allows separation of compounds according to their boiling point.

Furthermore, the gas produced in the reactor may be conveyed to a gas/solid separator such as a cyclone. Such a separator may be internal or external to the reactor. There may also be a plurality of internal and external separators in series, the purpose of which is to recover the reinforcement particles. Thus, solid particles entrained in the gas phase are filtered/separated either in the gas phase (before the condenser) or in the liquid phase (after the condenser).

In a third embodiment, the system suitable for recycling the first article 10 comprising a composite material based on fibrous reinforcement and a (meth) acrylic thermoplastic polymer matrix comprises a mixer-conveyor type device, for example a "paddle dryer" type mixer-conveyor. The apparatus comprises a reactor in which an impeller/rotating paddle is placed. The impeller thus allows mixing and homogenization of the mixture of the first and second products to be recycled. Mixer-conveyors have the advantage of allowing the handling of large quantities of solid waste/residues. It also allows good heat transfer between the wall and the waste. Such a device can be used at low temperatures to dry the solids (but in the context of the present invention, by increasing the temperature), depolymerization can be induced.

A fourth embodiment of a recirculation system 400 according to the present invention is shown in fig. 5. Such a system may include a rotating drum type device in which the entire reactor is rotated along a longitudinal axis. Alternatively, the drum is stationary and the rotating is an impeller/rotating paddle (paddle dryer type).

The drum type device advantageously comprises a reactor 450, the reactor 450 comprising an orifice 403 through which the first article 10 to be recycled passes, the first article 10 to be recycled comprising a composite material based on a fibrous reinforcement and a matrix of a thermoplastic polymer, preferably a (meth) acrylic polymer, which can be inserted, for example, by means of a metering device 410 and a conveying device 411. Similarly, a second article 20 to be recycled comprising a thermoplastic polymer, preferably a (meth) acrylic polymer resin, may be inserted, for example, by metering device 420 and conveying device 421. As previously mentioned, the reactor of the system according to the invention can take different forms, provided that the gas flow and the temperature can be controlled, and therefore the reactor of the system according to the invention can be adapted to a rotating drum type apparatus.

The first and

second articles

10, 20 to be recycled may be in powder or granular form or may have been crushed. In such an embodiment, the aperture 403 is arranged to receive a first article 10 to be recycled via the conveyor 411 of the metering device 410 and a second article 20 to be recycled via the conveyor 421 of the metering device 420.

In order to increase the yield related to the production of the base monomer from the thermoplastic polymer obtained from the

article

10, 20 to be recycled, the system 1 according to the invention may comprise a second reactor 480, the second reactor 480 being suitable for moderate heating of one of the

articles

10, 20 to be recycled. Advantageously, but not in a limiting manner, such a reactor 480 may correspond to a single-screw or twin-screw extruder 200 (as described in connection with fig. 3) and comprise one or two screws 404 rotating inside said second reactor 480.

In this embodiment, the reactor 480 comprises an orifice 401, through which orifice 401 said first and

second products

10, 20 to be recycled can be inserted, for example by means of the metering devices and conveying devices mentioned previously. Preferably, the second article 20 to be recycled is introduced via the orifice 401 of the reactor 480 and undergoes moderate heating during its passage inside said reactor.

As with the heating device of the twin-screw extruder 200, the external heating device 455 regulates the temperature of the reactor 450 and is advantageously configured to heat the second article 20 to be recycled and to bring the polymer resin into molten form without causing depolymerization. The temperature in the reactor can be between 200 ℃ and 350 ℃ and can also be controlled by means of a temperature sensor not shown in the figure.

This moderate heating advantageously allows to liquefy all or part of the polymeric resin of the article 20 to be recycled, so that said article is conveyed to the reactor 450 in the form of a viscous mixture via the orifice 402 arranged (to allow fluid communication between said reactors 450 and 480). Thus, the article 10 to be recycled is preferably added directly to the reactor 450 by mechanical or pneumatic transport after introduction of the article 20 to be recycled.

Further, the reactor 450 may include a driving source (not shown) that drives the reactor 450 to rotate around a fixed shaft 451 (in the case of a rotary drum), or a shaft 451 to rotate in the case of the reactor 450 of a paddle dryer type mixer-conveyor. Such a shaft 451 may advantageously comprise one or more movement means 452, or one or more mixing elements fixed along said shaft. Such movement means may advantageously take the form of paddles or impellers, having any geometry suitable for mixing the

products

10, 20 to be recycled. The movement means 452 thus allow the mixing and homogenization of the mixture of the first article 10 and the second article 20 to be recycled.

Suitable movement means are selected according to the type and size of the

products

10, 20 to be recycled, these products being in powder or granular form.

Finally, the reactor 450 may advantageously comprise an external heating device 455 which regulates the temperature of the reactor 450 and is configured to heat the

articles

10, 20 to be recycled and to melt the polymer matrix of the article 10 to be recycled and the polymer resin of the article 20 to be recycled. As previously described in connection with fig. 2, heating may also be staged, with a first heating zone at an intermediate temperature, followed by a second or second heating zone, and thus a plurality of heating zones at elevated temperatures.

In a similar manner to the system 1 described in connection with fig. 3, depolymerization may produce a product in gaseous form which is extracted from the apparatus for processing. In particular, the reactor 450 can be operated at a negative pressure or gas flow to convey the monomer formed to the condensation unit through the collection means. The generated gas may be directed to the recovery device 460 through the conduit 408 to be condensed. The obtained condensate may then be collected in a chamber 409 for this purpose.

The system presented in connection with fig. 5 may also comprise a purification device, not shown in the figures, which may correspond to a system for separation by distillation, for example a distillation column as described in connection with fig. 3.

Thus, once the

articles

10, 20 to be recycled are introduced and contacted in the reactor 450, they undergo depolymerization of their polymer matrix and polymer resin, respectively. In fact, the reactor 450 also comprises heating means 455, which are however advantageously configured to bring the parameterable temperature between 200 ℃ and 1500 ℃ and are suitable to induce depolymerization of the

products

10 and 20 to be recycled. The heating may also be performed in stages.

In addition to the fact of allowing to homogenize the

products

10, 20 to be recycled, the movement means 452 allow to facilitate the depolymerization of said products in the reactor 450 by promoting their contact.

In contrast to known drum systems, the system can advantageously be used in the absence of solids for promoting heat transfer, which is particularly suitable for recycling of composite articles.

It will be appreciated by the skilled person that the conveying means used are suitable for each embodiment of the recirculation system according to the invention, and are therefore particularly suitable for the use of paddle dryer type mixer-conveyors, rotary drums or twin-screw extruders. Similarly, it is contemplated that each embodiment of the system according to the present invention may include a recovery device 405, the recovery device 405 adapted for residues or solids from depolymerized articles to be recycled.

The invention will be further illustrated by the following examples. However, these examples should in no way be construed as limiting the scope of the invention.

[ examples of embodiments]

A]Preparation of composite materials with recyclable fiber reinforcement

Two compositions for compounding were prepared by dissolving PMMA beads composed of a copolymer of methyl methacrylate and acrylate. Preferably, the acrylate will be selected from methyl acrylate, butyl acrylate and ethyl acrylate.

Products of this type are commercially available, for example, from Altuglas as Altuglas BS series. Altuglas PMMA or acrylic glass is a typical material that complies with the principles of recycling and recycling because of its unique properties of being able to be depolymerized to methyl methacrylate and thus being able to be reintroduced into the process for making new resins.

The composition for compounding is prepared from recycled polymer. For example, injection molded PMMA components are used, such as tail lights for vehicles, or transparent panels for television flat panel displays or computer monitors. These elements were washed, dried and milled before being dissolved in methyl methacrylate.

The preparation of the different composites to be recycled C1, C2, C3 illustrated in the present invention is described below.

Example 1: composite material 1(C1)

In this example, PMMA beads consisting of a copolymer of methyl acrylate and Methyl Methacrylate (MMA) were used. 100 g of beads having an average particle diameter of from 0.150 to 0.200 mm, a density of 0.7 g/ml and a Tg ("glass temperature" Tg) of 107 ℃ are dissolved in 900 g of methyl methacrylate stabilized with 100 mg/kg of HQME (hydroquinone monoethyl ether).

To the dissolved mixture was added 10g of benzoyl peroxide.

To prepare the tested composite material, 600g/m of glass fiber fabric was used. The fabric was hand impregnated with a PMMA/MMA solution. The solution is applied to the mold with a brush or roller, and then the first fabric layer is applied. A new layer of solution is then deposited and spread out with a roller, which is also used to remove air bubbles, and the operation is repeated until ten layers of glass fibre fabric have been deposited. Finally an absorbent fabric to aid in demolding was placed. The whole was placed in a plastic bag, which was placed under partial vacuum (500mbar, i.e. negative pressure). The whole was then heated at 80 ℃ for 4 hours and then cooled to room temperature.

Example 2: composite material 2(C2)

Example 1 was repeated, but 200g of beads having a Tg of 110 ℃, an average particle size of 0.150 mm to 0.200 mm and a density of 0.7 g/ml were dissolved in 800 g of methyl methacrylate. To the mixture was added 10g of benzoyl peroxide. The other operations were the same as in example 1.

Example 3: composite material 3(C3)

In this example, 100kg PMMA plates were used, which were obtained from the deconstruction of flat screens for televisions and computers. Thus, the product is a product produced by a number of PMMA manufacturers, which has been produced for years and has a different but mainly asian origin, giving a kind of deconstructed product. The selected plates were relatively clean so as not to interfere with the testing, and the edges were trimmed to remove possible trace contaminants with adhesives, metals, and other polymers. The plates were ground into pieces of about one centimeter in size, then washed and dried. The product was then dissolved in 900kg of methyl methacrylate. Once dissolution is complete, the solution is filtered to remove foreign matter and any incompletely dissolved polymer. 10kg of benzoyl peroxide were then added. The composite was produced as in example 1, so as to consume all of the prepared solution.

The composite materials C1, C2, C3 were ground to reach a maximum dimension of 2 cm.

B]Configuration of disaggregation test

1) Laboratory test equipment

The laboratory reactor was a batch reactor with a working volume of 4.5 liters, having a cast iron pan with a capacity of 1.2 liters, on which a removable grate was mounted and which was electrically heated from the outside. The vapors generated during pyrolysis are condensed by cold traps installed in series. The first three wells were made of stainless steel and were maintained at 5 deg.C, 0 deg.C and-78 deg.C, respectively. The last well was made of borosilicate glass (Pyrex) and the temperature was maintained at-78 ℃. The non-condensable gases are led to the outside. Once the reactor is fed, it is purged under vacuum and/or nitrogen to remove molecular oxygen from the enclosure. The test was conducted under a vacuum of about 2.5 kPa.

2) Pilot plant

The pilot test was carried out in a cylindrical reactor 3m long and 0.6m in diameter, heated from the outside to avoid any condensation in the apparatus. The heating for the depolymerization reaction is carried out by a heating plate supplied with a heat transfer fluid. The product to be depolymerized is placed on a hot plate and flows through the device. The assembly comprises a supply system, a condensing unit, a system for discharging solid residues and a vacuum pump. In continuous mode, the system allows 50 kg/hour of feed. The test was performed in a "batch" mode in the first stage, considering the amount of composite material available. In this mode, the bed of product to be depolymerized is placed in a rectangular container on a hot plate, without using a residue feeding and extraction system.

The container is filled with the product to be depolymerized, weighed and placed in the reactor. The condenser functions by spraying pyrolysis gases and is initially filled with water. The condensed liquid is circulated through the apparatus to maintain a continuous flow in the condenser. When the apparatus is started, the air inside the reactor and in the peripheral equipment is evacuated by means of a vacuum pump. The reactor is then heated to the desired temperature.

The pyrolysis in the pilot reactor was carried out at 380 ℃ to 425 ℃ and a pressure of 2.1 kPa. The gas produced is rapidly cooled in two spray tower condensers connected in series. In the first condenser, the vapor is cooled by using a portion of the liquid that condenses at the bottom and is cooled with water. During the test, the excess liquid accumulated in the condensers was automatically drained into the tank connected to each condenser. The gases leaving the first condenser enter the second condenser where they are again contacted with the condensed liquid at the bottom of the condenser and cooled with water. The water condensed in the second condenser is separated by decanting the recovered product.

When pyrolysis stopped, heating was stopped and the pressure was increased up to atmospheric pressure by adding nitrogen to prevent any oxidation during cooling of the solids.

After the reaction, the mass of the residual solid and the mass of the collected liquid were measured to perform mass balance.

3)Sampling procedure:

the aqueous and organic phases collected in the laboratory or pilot condenser were decanted, separated and stored in a plastic tank. Representative samples were collected after homogenization. Prior to analysis, the samples were stored under cryogenic conditions and protected from light.

C]Depolymerization assay-laboratory assay

Example 4

200g of Altuglas HT121 resin particles having a density of 1.19 were placed in a depolymerization reactor. This product is available from Altuglas corporation.

Example 5

Example 4 was repeated with 200g of Altuglas HFI10 resin having a density of 1.15. This product is available from Altuglas corporation.

The reactor was subjected to a ramp to reach a constant temperature of 400 ℃ in 30 minutes. After 1 hour, the heating was stopped and the temperature was returned to room temperature. After stopping heating, the assembly was placed under a stream of nitrogen at atmospheric pressure for 2 hours. Once the temperature returns to below 50 ℃, the trap can be removed and the condensate weighed.

The polymer decomposition products were recovered for analysis. And (5) carrying out material balance. The mass of residual polymer was determined. The condensate trapped in the trap was weighed. The difference in quality is due to the light products (methane, light hydrocarbons, CO) resulting from cracking₂Etc.) also known as non-condensable gases.

The condensate is analyzed, in particular, by gas chromatography.

Examples 6 and 7

The above example was repeated with 300 grams of particles.

Examples 8 and 9

200g of the composite material from examples 1 and 2, respectively (C1 and C2, respectively), were used and ground to obtain chips with a maximum dimension of less than 2 cm. The milled composite was placed in a de-polymerization oven and the same protocol as in the previous example was applied.

Examples 10 and 11

The above example was repeated with 300 grams of composite material.

Examples 12 to 19

A mechanical mixture of composite material and resin particles is prepared. The mixture was placed in a plastic bag and homogenized by shaking until any visual heterogeneity was no longer distinguished. The depolymerization protocol was then repeated.

Good linearity of the decomposition products was observed for the same samples of 200g and 300 g. Within this scope, the apparatus is therefore not limiting in terms of heat and mass transfer.

[ Table 1]

Thus, the combined recycling of the first article to be recycled comprising fibrous reinforcement (C1, C2) and the second article to be recycled comprising thermoplastic polymer resin, preferably (meth) acrylic polymer resin, makes it possible to significantly increase the base monomer yield.

Thus, for the granular resin/composite mixture, a simple addition of depolymerized product (condensate) of quality higher than that obtained from the pure material was observed. It was furthermore observed that for experiments carried out under the same time constraints, the amount of MMA recovered was higher than the simple addition of the MMA mass obtained from the pure material. Thus, when preparing a mixture of composite material and injection or extrusion grade PMMA, the quality of the recovered product is better (for higher productivity). Thus, the mass of base monomer recovered by using the process according to the invention is indeed increased compared to the mass of base monomer recovered by the prior art techniques.

C]Depolymerization test-Pilot test

Pilot plant examples 20 to 23

About 20kg of milled composite or PMMA particles of type VM100 available from Altuglas, or a mechanical mixture of the two products, were placed in a metal container.

[ Table 2]

In pilot plant testing, a significant increase in the yield of base monomer was also observed.

The present invention therefore proposes a simple and effective solution for increasing the overall yield of the base monomer production during recycling of the composite article, in particular in the case where the first article comprises fibrous reinforcement and the monomer yield is low. The method according to the invention makes it possible to achieve recycling of articles comprising composite materials, the carbon footprint of which is reduced and therefore more environmentally friendly.

Claims

1. A method (100) for recycling a first article (10) to be recycled comprising a composite material based on a fibrous reinforcement and a thermoplastic polymer, preferably a (meth) acrylic polymer matrix, characterized in that it comprises the following steps:

-introducing (130) a first article (10) into a system (1) suitable for recycling thermoplastic polymers,

-introducing (140) a second article (20) to be recycled into a system (1) suitable for recycling thermoplastic polymers, the second article (20) to be recycled comprising a thermoplastic polymer resin, preferably a (meth) acrylic polymer resin, and no fibrous reinforcement,

-heating (150), in said system (1) suitable for recycling thermoplastic polymers, the articles (10, 20) to be recycled at a given temperature to depolymerize the thermoplastic polymers, preferably the (meth) acrylic polymers, and form the base monomers of said thermoplastic polymers, and

-recovering (160) the constituent base monomers of the thermoplastic polymer.

2. The recycling process (100) according to claim 1, characterized in that it comprises a step (170) of purifying the base monomer previously recovered.

3. A recycling method (100) according to claim 1 or 2, characterized in that it comprises a step (180) of removing solid components produced during the step of heating the first and second article (10, 20) to be recycled.

4. The recycling method (100) according to any one of the preceding claims, wherein the thermoplastic polymer matrix of the first article (10) is a poly (methyl methacrylate) matrix.

5. The recycling method (100) according to any one of the preceding claims, wherein said first article to be recycled (10) and said second article to be recycled (20) are introduced in a mass ratio of 0.1-1.5, preferably in a ratio of 0.1-0.5, more preferably in a ratio of 0.2-0.4.

6. A recycling method (100) according to any of the preceding claims, wherein the mass percentage of fibrous reinforcement of the first article (10) to be recycled is greater than 30%, preferably greater than 50%, more preferably greater than 70%.

7. A recycling process (100) according to any of the preceding claims, wherein the second article (20) is in the form of a slurry at room temperature and has a mass percentage of thermoplastic monomers, preferably equivalent (meth) acrylic monomers, of more than 80%, preferably more than 90%, preferably more than 95%.

8. A recycling process (100) according to any one of claims 1 to 6, characterized in that the mass percentage of thermoplastic monomers, preferably equivalent (meth) acrylic monomers, of the second article (20) to be recycled is less than 95%, preferably less than 90%.

9. A recycling process (100) according to any of claims 1 to 6, wherein the mass percentage of equivalent methyl methacrylate monomer of the second article to be recycled is less than 95%, preferably less than 90%.

10. The recycling method (100) according to any one of the preceding claims, wherein said system (1) suitable for recycling thermoplastic polymer resins is selected from:

-a depolymerisation system in the form of an extruder and/or a conveyor,

-a drum type depolymerization system, and

-a depolymerisation system on a hot plate.

11. A recycling method (100) according to any one of the preceding claims, wherein during said heating step the first and second articles (10, 20) to be recycled are heated to a temperature of 200-1500 ℃, preferably to a temperature of 300-600 ℃.

12. The recycling process (100) according to any one of the preceding claims, further comprising mild heating (151) of thermoplastic polymers, preferably (meth) acrylic polymers, to at least partially liquefy them.

13. A recycling method (100) according to any one of the preceding claims, comprising recovering (152) the fibrous reinforcement material of the first article (10) to be recycled, said recovering being carried out by at least one of the following methods: centrifugation, draining, spin-drying, pressing, filtering, screening and/or cyclonic separation.

14. A recycling method (100) according to any of the preceding claims, characterized in that it comprises a preliminary sorting step (120).

15. A recycling method (100) according to any of the preceding claims, characterized in that it comprises a grinding step (110).

16. A recycling process (100) according to any one of the preceding claims, wherein the second article (20) to be recycled comprises at least 50 mass% of a thermoplastic polymer, such as a (meth) acrylic polymer, more preferably at least 60 mass% of a thermoplastic polymer, such as a (meth) acrylic polymer, even more preferably at least 70 mass% of a thermoplastic polymer, such as a (meth) acrylic polymer.

17. A system (1) for recycling a first article (10) to be recycled, comprising a composite material based on a fibrous reinforcement and a thermoplastic polymer, preferably a (meth) acrylic polymer matrix, said system (1) being characterized in that it comprises:

-means (11) for conveying the first article (10) to be recycled,

-means (21) for conveying a second article (20) to be recycled comprising a thermoplastic polymer resin, preferably a (meth) acrylic polymer resin, and no fibrous reinforcement, and

-a reactor (50) suitable for heating the article (10, 20) to be recycled and depolymerizing the thermoplastic polymer, preferably the (meth) acrylic polymer, and forming the base monomers of the thermoplastic polymer.

18. A recirculation system (1) according to claim 17, characterized in that it comprises a second reactor (480), the second reactor (480) being adapted for moderate heating of one of the articles (10, 20) to be recirculated, preferably the second article (20) to be recirculated, said second reactor (480) comprising an orifice (402) arranged in fluid communication with the first reactor (450).

19. A recycling system (1) as claimed in claim 17 or 18, characterized in that it comprises means (60) for recovering the constituent basic monomers of the thermoplastic polymer.

20. A recirculation system (1) according to any of claims 17 to 19, characterized in that it comprises means (404, 452) for moving said first and second articles to be recirculated.

21. A recirculation system (1) according to any of claims 17 to 20, characterized in that the reactor (50) is an extruder or a conveyor.

22. A recirculation system (1) according to any of claims 17 to 20, characterized in that the reactor (50) is a pyrolysis reactor.